There is a parallel between Plato's argument for the forms at 74b7-c5 in the Phaedo and Frege's argument for the claim that proper names express senses. There is also, I claim, an important asymmetry. The asymmetry explains why it is consistent to accept the conclusion of the Phaedo argument without accepting the conclusion of Frege's argument. The Phaedo argument turns on the possibility of a specific kind of mistaken judgement that may be termed "brute error". Frege's argument does not so depend on the possibility of brute error.